As a communication apparatus for communication, such as a transmission apparatus and a switching equipment, there is used a bookshelf-type communication apparatus in which a plurality of printed-circuit board units (hereinafter referred to as plug in units (PIUs)) having signal processing circuits such as electronic circuit packages are mounted on a back wiring board (BWB) installed on the rear of a metal shelf (i.e. case).
In recent years, more numbers of PIUs may be mounted on one communication apparatus. Furthermore, long-distance and speeding up (in other words, improvement in transmission performance) for the transmission of a signal on the BWB may be preferred. As one example of method for the improvement in transmission performance, there has been suggested a method for mounting a waveform shaping function, such as a FFE (Feed Forward Equalizer) function performed on the signal transmission side and a DFE (Decision Feedback Equalizer) function performed on the signal reception side, on the PIU in a Serdes (Serializer/De-Serializer) circuit used in the signal transmission/reception.    Patent document 1: Japanese Patent Application Laid Open No. 2001-268978